1. Associated Hazards and Safety Practices
REVENUE METERING
Associated Hazards
and
Safety Practices

2. Transformer-rated Meters
Application and Components
Current Transformers
Voltage (Potential) Transformers
Transformer-rated meters are used because: Meters used directly on high voltages (over 480V) or currents (over 200A) could fail or explode.

3. Transformer-Rated Meters (cont.)
Components
Instrument transformers
Test switches
Transformer-rated revenue meter
Transformer-rated meter base

4. Current Transformers For customers who use over 200 amps. Types Bar
Window
Switchgear
Primary

5. Current Transformers (cont.)
Ratio (Multiplier) _% of energy sent to meter.
A common ratio is 200:5. This means that there is a multiplier of 40.
Burden: Expressed in ohms and tells you the load on the secondary.
Rate Factors: Thermal:
How much the primary load current can be increased over it’s nameplate value.

6. Current Transformers: Nameplates
Shorting Bar X1 X2
Voltage Rating
Ratio
Rate Factor
Ratio

7. Current Transformers (cont.)
Construction
Shunting bar
Primary (H1 or H2); Secondary (X1 or X2)
Larger wire/few turns; smaller wire, many turns
Lower current on output for meters

8. Current Transformers (cont.)
Dangers of CT’s If you open the connections in a CT meter: The voltage across the secondary will increase rapidly toward infinity, which may cause the CT to explode.
WARNING!
Never open the connections in a CT meter

9. Current Transformers Connection
Customer

10. Current Transformers Connection
What happens when you take the meter out of the circuit? ?
Customer

11. Current Transformers Connection
A voltage is still induced onto the secondary windings of the CT. This leaves an open circuit.
What happens when you take the meter out of the circuit?
Customer
Customer is still energized!

12. Current Transformers (cont.)
Opening a CT
Pull the meter
Cut the secondary wire to meter
Any way that opens the current path between the secondary of the CT to its return.

13. Voltage Transformers (VT or PT)
Step down the primary voltage to lower levels that are safer and easier to meter.
PT = VT
Transformers are connected to the service voltage.
Connected in parallel

14. Voltage Transformers (VT or PT)
Typically used on systems with more than 600V.
Transformers are connected to service voltage.
Ratio: Percent of voltage sent to meter
Burden: Expressed in VA and relates to the load on the secondary side of the potential transformers.

15. Voltage Transformers (cont.)
Types of VTs
Primary
Secondary
Rating VTs
W= 12.5 va
X = 25 va
Y = 75
Z = 200
Zz = 400
M = 35

16. You are dealing with voltage (not current)
Dangers of PTs
Never shunt a PT
You are dealing with voltage (not current)
and you are connected in parallel (not series).

17. Types of Meter Bases Bypass Meter Bases
Safety Sockets -energized or not?
Green lever vs. red lever
Jaws open but can be bypass
Bypasses not designed to carry full load
Cut off levers for current diversion
Test switch provisions -transformer rated

18. Installing and Removing Meters
Be safe!
If hazards are present, do not
work alone.
When installing or removing the first priority is:
ENSURING
YOUR SAFETY!

19. Installing and Removing Meters (cont.)
Never pull a meter under load.
Disconnect meter by shutting off breaker.
Verify that the power is disconnected at:
The weatherhead.
The transformer.
Re-installing meter under load will cause sparking.

20. Installing and Removing Meters (cont.)
Pulling transformer-rated meter without shunting current transformers
Current transformers may explode!
Customer will still be in power.

21. Socket Checks Determine if socket is wired correctly.
Verify no backfeed or fault condition exists.
Use meter socket check handout.
Inspect for any missing knockouts or openings to energized equipment.

22. Socket Checks (cont.) Inspect for broken/misaligned socket terminals.
Inspect for broken/cracked porcelain blocks.
Ensure the socket base is properly secured and meter can be sealed.

23. Meter Installation Notify customer Use proper safety gear Socket check
Visual inspection

24. Meter Removal
A meter is not a load break tool! Deenergize the meter before pulling it.
Notify customer
Use proper safety gear
Verify no load
Visual inspection

25. Meter Selection Issues
Typical misapplication of 5 point meter
Wild leg in the wrong spot
Single phase 120/240 vs120/208 (2S vs. 12S)
Older 14S 240 volt meters -Actual voltage 277/480
120 volt 1S meter in a 240 volt 2S service

26. Detecting Current Diversions

27. Detecting Current Diversions

28. The photo on the top shows a 5-terminal lever bypass socket used with a Form 12S, 480 volt meter on 480 volt, 3 wire delta application
The photo on the bottom shows the existing meter “can” retrofitted with a TS-SCB-1 block assembly and VT Pack. The VT Pack is mounted on the outsie of the socket with the CK-St-1 mounting kit.

29. Any Questions?